Involved in the transport of ions, molecules, and other substances across a membrane.
Without a transport protein, cells can only perform simple diffusion. Channel proteins use facilitated diffusion, and Carrier proteins do both facilitated diffusion and active transport.
There are two types of transport proteins:
Channel Proteins
Carrier Proteins
Channel Proteins always utilitize Passive Transport (do not require energy), while Carrier proteins may use Passive or Active Transport (requires energy).
Facilitated Diffusion:
Passive transport
Follows the concentration gradient; i.e., it moves molecules from an area of high concentration to an area of low concentration
Both Channel Proteins and Carrier proteins
A Channel protein has a channel through which the water molecules or a specific solute can pass
A Carrier protein changes shape, moving the molecules across the membrane during the change In both cases, the net movement is down the concentration gradient
Active Transport
Goes against the concentration gradient, therefore requiring energy-- usually gets this energy by decomposing ATP into ADP by dephosphorylation
ATP- Adenosine Triphosphate, supplies the energy for most active transport. It decomposes into Adenosine Diphosphate, and the "freed" phosphate releases energy and allows the active transport to occur.
Active Transport Protein (ATP)
What is happening above:
The sodium within the cell binds to the carrier protein, stimulating dephosphorylation by ATP. The Sodium is then expelled from the cell, while potassium enters the cell, and ADP is formed
Examples of Carrier Proteins:
Diffusion of sugars
Uptake of glucose
Transportation of salts
Examples of Channel Proteins
Voltage-gated ion channel, such as potassium channel
Chloride channels
Aquaporins
Research on Cell Membrane Transport Proteins
Dr. James Young, University of Alberta. Young Studies proteins that transport nucleosides and nucleobases into and out of cells, mostly by injecting genetic messages from humans and other organisms into unfertilized frog eggs, and observing the response. Website
Kenny Linton, Medical Research Council (MRC) Clinical Sciences Centre, Imperial College London, London, UK. Studying structure and function of
ABC (ATP- binding cassette) transporters in cells. Website
Works Cited Campbell, Neil A. Biology. 8th ed. San Francisco: Pearson Education, Inc., 2008. “Membrane Transport Protein.” Biology Online.13 Oct. 2008 <http://www.biology-online.org/dictionary/Membrane_Transport_Protein>. “Membrane transport protein.” Wikipedia, the free encyclopedia. 10 Oct. 2008.13 Oct. 2008 <http://en.wikipedia.org/wiki/Membrane_transport_protein>. Sansom, Mark. “Ion Channels and Membrane Transport Proteins.” Laboratory of Molecular Biophysics. 8 Jan. 2001. Oxford University.14 Oct. 2008 http://biop.ox.ac.uk/www/lj2000/sansom/sansom.html.
Membrane Proteins--Transport
Involved in the transport of ions, molecules, and other substances across a membrane.
Without a transport protein, cells can only perform simple diffusion. Channel proteins use facilitated diffusion, and Carrier proteins do both facilitated diffusion and active transport.There are two types of transport proteins:
- Channel Proteins
- Carrier Proteins
Channel Proteins always utilitize Passive Transport (do not require energy), while Carrier proteins may use Passive or Active Transport (requires energy).Facilitated Diffusion:
- Passive transport
- Follows the concentration gradient; i.e., it moves molecules from an area of high concentration to an area of low concentration
- Both Channel Proteins and Carrier proteins
A Channel protein has a channel through which the water molecules or a specific solute can passA Carrier protein changes shape, moving the molecules across the membrane during the change
In both cases, the net movement is down the concentration gradient
Active Transport
ATP- Adenosine Triphosphate, supplies the energy for most active transport. It decomposes into Adenosine Diphosphate, and the "freed" phosphate releases energy and allows the active transport to occur.
What is happening above:
The sodium within the cell binds to the carrier protein, stimulating dephosphorylation by ATP. The Sodium is then expelled from the cell, while potassium enters the cell, and ADP is formed
Examples of Carrier Proteins:
- Diffusion of sugars
- Uptake of glucose
- Transportation of salts
Examples of Channel ProteinsResearch on Cell Membrane Transport Proteins
ABC (ATP- binding cassette) transporters in cells. Website
Works Cited
Campbell, Neil A. Biology. 8th ed. San Francisco: Pearson Education, Inc., 2008.
“Membrane Transport Protein.” Biology Online. 13 Oct. 2008 <http://www.biology-online.org/dictionary/Membrane_Transport_Protein>.
“Membrane transport protein.” Wikipedia, the free encyclopedia. 10 Oct. 2008. 13 Oct. 2008 <http://en.wikipedia.org/wiki/Membrane_transport_protein>.
Sansom, Mark. “Ion Channels and Membrane Transport Proteins.” Laboratory of Molecular Biophysics. 8 Jan. 2001. Oxford University. 14 Oct. 2008 http://biop.ox.ac.uk/www/lj2000/sansom/sansom.html.